In general, an optical image sensor is a semiconductor device that converts an optical image to an electrical signal. Optical image sensors can largely be divided into charge coupled devices (CCD) and complementary metal oxide semiconductors (CMOS).
A CMOS image sensor incorporates a photo diode for detecting radiated light and a CMOS logic circuit that processes the detected light into electrical signal data. The more light a photodiode is capable of detecting, the better the image sensor's photosensitivity characteristics are.
The CMOS image sensor can be categorized by the number of transistors for each unit of the CMOS image sensor such as, for example as a 3T-type, a 4T-type, or a 5T-type.
Below, a manufacturing method of a CMOS image sensor according to the related art will be described, with reference to the diagrams.
FIGS. 1A through 1D are sectional views showing a manufacturing process of a CMOS image sensor according to the related art.
Referring to FIG. 1A, a plurality of light detecting modules, for example, photodiodes 12 are formed on a semiconductor substrate 11, on which an interlayer insulating layer 13 is formed.
Then, a dye resist is applied on the interlayer insulating layer 13, and exposing and developing processes are performed to form a color filter layer 14 with filters for filtering respective ranges of wavelengths.
Next, in order to adjust the focal distance and to form a lens layer on the color filter layer 14, a planarizing layer 15 is formed for ensuring flatness.
Referring to FIG. 1B, a resist layer 16a for forming a microlens is applied on the planarizing layer 15, and a reticle 17 having openings is arranged above the resist layer 16a. 
Then, a laser is emitted through the reticle 17 to selectively expose the resist layer 16a corresponding to the openings of the reticle 17.
Referring to FIG. 1C, the exposed resist layer 16a forms a microlens pattern 16b. 
Referring to FIG. 1D, the microlens pattern is made to reflow at a predetermined temperature to form the microlens 16.
Here, A and B denote respective spaces formed between microlenses 16. Because of the difficulty of controlling the reflow process, differences in critical dimension (CD) spaces arise between each microlens 16.
Therefore, the manufacturing method of a CMOS image sensor according to the related art has the following problem.
When a reflow process is performed to form dome-shaped microlenses, the CD spaces (A and B) are not uniform, resulting in a striation phenomenon of the microlenses.